In addition to confirming the well-publicized high antioxidant ranking of such foods as cranberries and blueberries, the researchers found that Russet potatoes, pecans and even cinnamon are all excellent, although lesser-known, sources of antioxidants, which are thought to fight cancer, heart disease and Alzheimer's.
The new study, which appears in the 9 June edition of the Journal of Agricultural of Food Chemistry (vol 52, issue 12, pp 4026 - 4037), is more complete and accurate than previous data produced by the US Department of Agriculture, thanks to updated technology.
However Ronald L. Prior, a chemist and nutritionist with the USDA's Arkansas Children's Nutrition Center and lead author of the study, warned that total antioxidant capacity of the foods does not necessarily reflect their potential health benefit, which depends on how they are absorbed and utilized in the body.
Researchers are still trying to better understand this process.
Currently, there are no government guidelines for consumers on how many antioxidants to consume and what kind of antioxidants to consume in their daily diet, as is the case with vitamins and minerals. A major barrier to such guidelines is a lack of consensus among nutrition researchers on uniform antioxidant measurements.
Scientists meeting this week in Florida at the First International Congress on Antioxidant Methods are however trying to develop a consensus, with the ultimate goal of developing better nutritional data for consumers.
The new data also includes more foods than the previous study, revealing antioxidant levels in over 100 different foods, and it includes data on spices and nuts for the first time.
Although spices are generally consumed in small amounts, many are high in antioxidants. On the basis of antioxidant concentration, ground cloves, ground cinnamon and oregano were the highest among the spices studied.
Among the fruits, vegetables and nuts analysed, each food was measured for antioxidant concentration as well as antioxidant capacity per serving size.
Cranberries, blueberries, and blackberries ranked highest among the fruits studied. Beans, artichokes and Russet potatoes were tops among the vegetables. Pecans, walnuts and hazelnuts ranked highest in the nut category.